30-m Telescope System Summary
(September 2007)

 

Receiver Parameters

A maximum of four receivers, from the total of eight, can be used simultaneously. The following table summarizes the allowed combinations and some of the most important receiver characteristics. Plots of the receiver characteristics. HERA cannot be combined with other receivers; up to now not all frequencies have been pretuned. Hera has 18 pixels separated by 24". Local contact for HERA: Albrecht Sievers

Rx
Pol.
Rx combinations
tuning range
(GHz)
T_rec
(K)
IF
(GHz)
IF-BW
(GHz)
g_im
(dB)
Remarks

A100

V



80-115.5
60-80
1.5
0.5
>20

1

B100

H



81-115.5
60-85
1.5
0.5
>20

1

C150

V



130-183
70-125
4
1
15-25

 

D150

H



130-183
80-125
4
1
08-17

 

A230

V



197-266
85-150
4
1
12-17

 

B230

H



197-266
95-160
4
1
12-17

 

C270

V



241-281
125-250
4
1
10-20

2

D270
H


241-281
150-250
4
1
09-13
2

HERA

H
V





215-272
215-241
110-380
120-340
4
1
~10

2, 3

1) Using a special external LO, frequencies down to 77 GHz can be measured with good sideband rejection. For frequencies below 77 GHz,
the sideband recection becomes weaker, and the sideband ratio reaches unity at 72 GHz
2) Noise increasing with frequency
3) 2x(3x3) pixel receiver with a 24" separation of the pixels. Equipped with a derotator allowing to follow a source in the sky maintaining the same "footprint".

Bolometer Parameters

Bolometer Beam Lambda Pixels Spacing between Horns rms after 10 minutes (normal bolometric conditions) with skynoise removal
MAMBO I 11" 1.2 mm 37 20" 1.5 mJy
MAMBO II 11" 1.2 mm 117 20" 1.5 mJy

local contact for bolometers: Stephane Leon

 

Efficiencies and Half-power beam width

Below you find the most recent values for the forward and beam efficiencies. We have also compiled the value of the efficiencies in the past .

Here you can find the plot with the most recently measured beam efficiencies.

freq (GHz)

HPBW('') 1)

B_eff 2)

S/T_A* 3) (Jy/K)

72 (extrapolated) 34 0.79 6.0
77 (extrapolated) 32 0.79 6.0

86

29

0.78

6.0

110

22

0.75

6.3

145

17

0.69

6.7

170

14.5

0.65

7.1

210

12

0.57

7.9

235

10.5

0.52

8.7

260

9.5

0.46

9.5

279

9

0.42

10.4

 

1) The HPBW can be well fit by: HPBW('') = 2460/freq(GHz).

2) The data can be well fit by a Ruze function B_eff = 1.2 epsilon exp[-(4pi R sigma/ lambda)^2] with sigma being the rms value of the telescope optics deformations, R the reduction factor for a steep main reflector, epsilon the aperture efficieny of the perfect telescope and lambda the wavelength in mm. The data can be fit by R*sigma = 0.07 and epsilon = 0.69. The aperture efficiency of the 30-m telescope can be obtained using eta_a=B_eff*0.79

3) For a Gaussian source and beam size, and a source which is much smaller than the beam, S(Jy)/T_mb(K)=8.18E-7*theta(")^2*nu(GHz)^2 (Rohlfs & Wilson, Tools of Radioastronomy (2. ed., Eq. 8.20). Using the approximation in 1) yields for the 30-m telescope S/T_mb=4.95 Jy/K. S/T_A* is obtained by multiplying 4.95 J/K with F_eff/B_eff

Receiver

F_eff 4)

A100/B100

0.95

C150/D150

0.93

A230/B230

0.91

C270/D270

0.88


4) The values for F_eff are valid after the 12th of December 2000 when a new reflecting ring was put around the secondary mirror. The moon efficiencies are equal to forward efficiencies (Kramer et al. 1997).

Spectral Line Backends


Resolution

Bandwidth

Receiver (width mode)

Remark

1 MHz Filterbank

1 MHz

4x256 MHz
2x512 MHz or
1x1GHz

A100, B100 (narrow)
A230, B230, C150, D150,
C270, D270 (narrow or wide)

max 4 parts; series parallel or mixed mode possible; using the filterbanks with 1GHz bandwidth excludes the use of the AC or the 100 MHz FB with the same rx. The FB can be shifted in multiples of 32 MHz from the center frequency of the connected rx.

4 MHz Filterbanks

4 MHz

9x1GHz

either HERA1 or HERA2 (wide),
all other SIS receivers (wide) except 3mm


max 9 parts; use of the 4 MHz FBs excludes the use of the AC or the 100kHz FB on the same receiver. Frequency switching not available. While the channel spacing is 4MHz, the 3dB width is 5.4 MHz and the noise equivalent width is 6.5 MHz

100 kHz Filterbank

100 kHz

2x12.8 MHz or
1x25.6 MHz

 all SIS receivers (narrow) except HERA

The FBs can be moved within a 500 MHz band and connected to 1 or 2 rx.
Decommisioned (12.9.2007)

WILMA 2 MHz 18x930 MHz  HERA (wide)
 
VESPA 3.3 kHz-1.25 MHz 10-512 MHz  all SIS receives incl. HERA (narrow)
Up to 18000 channels. In connection with HERA (9 pixels) the following combinations of resolution (kHz) and bandwidth (MHz) are possible: (20/40), (40,80), (80, 160), (320,320), (1250, 640); local contact: G. Paubert
XPOL 40kHz-1.25MHz 120-640MHz  A100 and B100 (narrow)

Spectral line polarimeter which uses VESPA to determine the four Stokes parameters


Spectral Line Observing Modes


Created by R. Mauersberger , December 17, 1999, last change Sep. 12, 2007, by RM